1. Field
The present invention is a washing machine, and more particularly to a washing machine with a power transmission device to intermittently control power transmission between a washing shaft and a dehydrating shaft according to a rotated position of the washing shaft.
2. Description of the Related Art
Generally, a washing machine is an apparatus which washes laundry by performing a washing cycle, a rinsing cycle and a dehydrating cycle while rotationally operating a dehydrating tub mounted in a water tub, and a pulsator. In such a washing machine, the dehydrating tub is mounted in the water tub that holds wash water therein, and the pulsator is mounted to a lower part of the dehydrating tub to agitate the laundry and the wash water in the dehydrating tub.
In addition, a driving motor and a power transmission device are further included in a washing machine. The driving motor is mounted to a lower part of the water tub. The power transmission device is provided to transmit a rotational force of the driving motor to the dehydrating tub and the pulsator.
An example of the washing machine with a power transmission device is disclosed in KR Patent Laid-open No. 2003-34364. According to the disclosure, the power transmission device is equipped with a float such that power transmission to a pulsator and a dehydrating tub can be intermittently controlled according to the operation of the float by buoyancy of the wash water held in the water tub.
Furthermore, KR Patent Laid-open No. 2004-104979 discloses another example of a washing machine equipped with another type of the power transmission device. According to this reference, the power transmission device controls the power supply, being driven by a clutch motor dedicatedly provided beside the driving motor.
However, the above conventional power transmission devices of the washing machine have the following problems.
First, the power transmission device in the first example uses buoyancy of the wash water as a rotational force to operate the power transmission device. Therefore, since the power transmission can be controlled in accordance with water supply performed by the water tub without a dedicated power source, the structure is simplified. Nevertheless, the volume of a dehydrating tub should be increased compared to the capacity of the washing machine in order to generate an air layer in the water tub. Furthermore, a sufficient space needs to be secured between the water tub and the dehydrating tub for vertical movements of the dehydrating tub in the space. Accordingly, consumption of water is greatly increased.
Second, the power transmission device using the clutch motor of the second example guarantees high reliability of the power transmission control. However, since a complicated mechanical structure including the dedicated clutch motor is required, the production cost is increased.